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2005 yukon xl thermostat question

Discussion in 'GM Powertrain' started by Pikey, Dec 31, 2013.

  1. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    Hi Guys and Girls,
    I have a 2005 yukon xl with a 5.3L. I replaced the thermostat last summer. Here is the issue that I am seeing now. (may not be an issue) I can start the truck and drive it, it warms up to operating temperature as it should. But, when just idling it does not get to the operating temp. I can drive it at operating temp and all is fine. When I idle for around 5 minutes the temp drops significantly. (it is 15 degrees here now) When I start driving the temp goes right back up to where it should be within a mile or so. So, my question is, should I put a new t-stat in it again? I have owned 3 5.3L and never noticed this before. @j cat , @RayVoy, @99'HEARTBEAT , opinions guys? everyone else feel free to chime in.
    here is a pic of just above where it drops to, it goes to the line just below the needle. it is the lower right gauge :

    View attachment 1231132101.jpg
    Last edited: Dec 31, 2013
  2. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    Mike....I also replaced the thermostat back in August of this year, and once my Engine a "5.3L" is up to Normal Operating Temps, Gauge reads around, 180/190 Degrees...and as far as I can tell, it doesn't drop like yours.

    By chance do you have anyway to check with a DTC Reader, with a Scanner, so you can see some Live Logging Data for the Gauge??
  3. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    I do have a Jet programmer with a monitor function. It reads a lower temp at idle. looks like I may replace the t stat later this morning. I need to see if one of the managers I know at the parts store is working so they can warranty it for me. Oddly, I can not find that receipt.
  4. RayVoy

    RayVoy Active Member 1000 Posts 100 Posts

    Mike, I think Mike (@99'HEARTBEAT) has the right suggestion (and he beat me, haha). It does sound like the t-stat is not closing to hold the heat in the engine.

    Did you guys have a good New Year's eve?
  5. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts


    Morning Ray, and Happy New Year, it was a quiet one for me and my wife, and how was yours??

  6. RayVoy

    RayVoy Active Member 1000 Posts 100 Posts

    We had planned to have a couple of couples over, but, as it turned out, it was the coldest night this winter and they decided to stay home. I don't blame them, they had a 10 mile drive and no one wanted to get into a cold car at 2am.

    So, I watched "the festivities on tv and was asleep by 1am (Margot didn't make 12am, haha).
  7. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    I changed out the t-stat this morning. After a quick test drive I let it idle in the garage for a few minutes and the temp dropped to 170.5. I topped off the coolant and drove it around for a while. I let it idle with the heaters (front and rear) on full blast for 20 minutes. The lowest it went on my monitor was 185.0 as soon as I touched the gas it dropped to 183.2. I drove around and while driving it is at 199.2 to 205.0 depending on how much I am on the gas. As of right now I am calling it fixed. I guess I will see over the next few days. Thanks for the help guys!
  8. 99'HEARTBEAT

    99'HEARTBEAT Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts


    Ya Mike, It sounds like got this issue fixed........BTW Happy Year!!....:party:
  9. RayVoy

    RayVoy Active Member 1000 Posts 100 Posts

    Happy New Year [MENTION=51590]Pikey[/MENTION]
  10. Pikey

    Pikey Moderator Staff Member 1000 Posts 100 Posts

    Happy New Year Guys! :party:

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